This project is a continuation of a taxonomic study, begun in 1951, of the more rapidly growing mycobacteria, the nocardias, and the streptomycetes. The continuation project proposes (1) to identify specifically the remaining strains in our collection plus those requested from or sent to us by other investigators by a group of morphological, physiological, and chemical (chromatographic analyses of whole-cell hydrolysates) characteristics believed to be distinctive for each species; (2) to publish descriptions of the remaining species when they are adequately represented in our collection; and (3) to make our strains and data available to and thus assist other microbiologists interested in the three related genera, Mycobacterium, Nocardia, and Streptomyces.